The present invention relates to a spacer for wire reinforcement used in the manufacture of welded wire reinforced concrete articles such as pipe, and more specifically to a spacer for maintaining concentric wire reinforcement cages in spaced relationship from each other and the pipe form when concrete is formed around the wire reinforcement.
A wire reinforcing assembly typically comprises wire fabric formed to generally conform to the shape of the article being produced. For example, in manufacturing a wire reinforced concrete pipe, the fabric is shaped into a generally cylindrical cage having a smaller diameter than the outer cylindrical pipe form in which the pipe is to be cast. Often, a second cylindrical cage having a diameter somewhat smaller than that of the first cylindrical cage is included to further reinforce the concrete pipe.
In the manufacture of a wire reinforced concrete pipe, it is important that the cage assembly be located in the pipe form a spaced distance from the pipe form wall or walls. When a single external wall form is used and the pipe is dry cast in a packer head machine, the cage assembly must be spaced from the external wall. When a double wall form is utilized and the concrete is to be cast around the cage assembly, the assembly must be spaced from both the inner and outer walls. Further, to insure the structural integrity of the pipe, it is important that the two cylindrical cages in the assembly be maintained in fixed concentric relationship with respect to each other during manufacture. Various spacing devices exist in the prior art for performing these spacing functions, but none is completely satisfactory.
Often, the two concentric cages are tied with wire ties to common spacer bars oriented generally radially with respect to the cages. These spacer bars extend radially outwardly beyond the outer cage and/or radially inwardly beyond the inner cage to engage the pipe form to maintain the cage assembly in proper spaced orientation within the form during casting. Alternatively, the spacer bars can be welded to the cylindrical cages. In any event, the attachment of these spacer bars to the cages is extremely time consuming, whether they are tied using wire ties or welded. Additionally, the unfinished rod ends which engage the pipe form to space the assembly from the form may scratch, or score, the form destroying its smooth surface. Further, these rods can be bent when the cage assembly is inserted into the form or during subsequent casting, which destroys the desired accurate spacing between the cage and the pipe form.
Another spacer for maintaining cylindrical cages in concentric relationship includes an elongated spacer member having a J-hook at one end and a C-hook at an opposite end. (U.S. Pat. No. 3,440,792 to Schmidgall which issued Apr. 29, 1969) The J-hook is looped around a wire of one cage while the C-hook is cammed onto a wire of the second cage. A portion of the C-hook extends beyond the second cage to engage the pipe form. However, because the spacers include no locking structure at either one end, they do not positively retain the inner and outer cages in fixed relation. Further, because the spacer includes structure at only one end of the elongated member for spacing the cage assembly from the form, these spacers must be carefully alternated in orientation on the inner and outer cages to provide proper spacing within the pipe form.
Yet another spacer includes a bent metal member having first and second flanges extending from opposite sides thereof. The flanges are welded to inner and outer cages in order to properly maintain the inner and outer cages in proper orientation with respect to each other. The required welding is extremely time consuming and expensive. Further, these spacers do not include any provision for spacing the assembly from either of the form walls. Therefore, either the cage assembly is not properly oriented within the form or additional spacing means must be installed on the assembly in order to properly orient the assembly within the form.